function sigma2 = eq_sigma2_1(T,W)
a_v = 15.55493;
k_v = 20.64504;
a_t = 0.02332;
k_t = 0.0261;
index = (a_t+k_t*W)*T-a_v-k_v*W;
sigma2 = pi*pi/(100*100)*(1+exp(index));